Aquaria is an Underwater Fantasy adventure game by the indie company bit-blot.
A Windows versions was already done and they are now working on the GNU/Linux client that will be released soon.

An Underwater Fantasy World to Explore
A massive ocean world, teeming with life and filled with ancient secrets. Join Naija, a lone underwater dweller in search of her family, as she explores the depths of Aquaria. She’ll travel from hidden caves, shrouded in darkness, to beautiful, sunlit oases, all lovingly handcrafted by its two creators.
Naija’s story, narrated fully with voice overs, will become yours, as you join her on this magnificent adventure.

Magic and Combat at a Mouse-Click
Naija has the gift of the Verse. By singing songs, she can weave this force to change the waters around her. With each song Naija learns comes new abilities. With powerful songs, Naija is able to change form, giving players many options as to how to play the game.
And with Aquaria’s intuitive mouse-only control system, it’s as easy to make Naija swim gracefully through the waters as it is to have her sing, cast spells, and engage in combat with the numerous dangerous creatures that inhabit Aquaria’s waters.
The Xbox 360 controller and FPS style mouse / keyboard controls are also supported.

Create Your Own Worlds
The full version of Aquaria includes the level editor and modding tools which we used to develop the game. Easy to pick up and learn, you’ll be able to make your own worlds, and even add your own graphics and music. The powerful Aquaria level editor allows you to test your creations while you play the game!

World
The world of Aquaria hides the secrets of creation within its depths. The currents that buffet the many diverse plants and animals that live there also carry with them stories of long lost civilizations; of love and war, change and loss.
From lush, green kelp forests to dark caves, exploring will be no easy task. But the splendor of the undersea world awaits Naija… and you.Crystalline Blue
The glassy waters of the open sea let you peer far into the distance, and fish and other creatures play beneath the wide canopies of giant, undersea mushrooms.
Here, ruins serve as a clue to Aquaria’s long past. Will they lead Naija to the truth?The Natural World
The kelp forest teems with life. As light from above pours across the multitudes of strange plants and animals that live here, one cannot help but marvel at the dynamic landscape.
But beware, its beauty belies the inherent danger inside. Careful not to lose your way.Darkness
As you swim deeper, to where sight cannot reach, the Abyss begins to swallow you whole. The deeper waters of Aquaria have spawned legends of frightening monstrosities that lurk where few things can survive. Are they true????
What lies beyond? Are there areas deeper than the Abyss? Or as we swim ever upward, can we find the source of the light?
Only those with great fortitude will come to know and understand the mysteries of Aquaria.